The Evidence For Evolution: A Succinct Introduction For Denialists

By R.N. Carmona

In the U.S., there are a few striking examples of science denialism. Perhaps the most troubling among these instances is the rejection of evolution. Fundamentalist Christians have fought to keep evolution out of schools and have fought equally as hard to push creationism and/or Intelligent Design (ID) into the classroom. According to a 2014 Gallup poll, 42% of Americans deny evolution and accept creationism. Given this, it is imperative to be capable of explaining evolution and the evidence in support of it. Having this capacity does not ensure that denialists will come to accept it. There’s still the issue of comprehension; there is, in other words, a pervasive problem arising from two distinct and yet related facts: science denialists are not familiar with the relevant jargon and thus, cannot comprehend, for instance, an informal argument for evolution; science denialists usually have a disdain for both alternative opinions and reading and therefore, would forego reading a piece defending an alternative opinion. On that last issue, they would much rather accuse an “evolutionist” of lacking substance or not being an expert–despite the fact that said individual is citing experts and reputable sources. Given this, it is necessary to be brief and effective when presenting the evidence for evolution. This is what I’ll endeavor to do here.

There are a number of lines of evidence for evolution: biogeographic distribution, homologies, atavisms, vestigial organs and traits, and perhaps the most compelling stemming from genetics: GLO (short for gulono-y-lactone oxidase) and ERVs (endogenous retroviruses), which will be discussed at length. Since I am not an expert and I am sans pretenses to the contrary, I will cite reputable sources and experts in order to make a brief case. Since the evidence for evolution is vast and requires a grasp of multiple sciences–e.g., paleontology, anthropology, genetics, evolutionary biology, environmental science–I will narrow my focus and speak only of the evidence that is arguably most compelling. I will begin with GLO, which is a pseudogene or a non-functional gene. Jerry A. Coyne, Professor of Biology at the University of Chicago, provides one of the better evidences of evolution:

The most famous human pseudogene is GLO, so called because in other species it produces an enzyme called L-gulono-y-lactone oxidase. This enzyme is used in making vitamin C (ascorbic acid) from the simple sugar glucose. Vitamin C is essential for proper metabolism, and virtually all mammals have the pathway to make it — all, that is, except for primates, fruit bats, and guinea pigs. In these species, Vitamin C is obtained directly from their food, and normal diets usually have enough. If we don’t ingest enough vitamin C, we get sick: scurvy was common among fruit-deprived seamen of the nineteenth century. The reason why primates and these few other mammals don’t make their own vitamin C is because they don’t need to. Yet DNA sequencing tells us that primates still carry most of the genetic information needed to make the vitamin.

It turns out that the pathway for making vitamin C from glucose involves a sequence of four steps, each promoted by the product of a different gene. Primates and guinea pigs still have active genes for the first three steps, but the last step, which requires the GLO enzyme, doesn’t take place: GLO has been inactivated by a mutation. It has become a pseudogene, called ΨGLO (Ψ is the Greek letter psi, standing for “pseudo”). ΨGLO doesn’t work because a single nucleotide in the gene’s DNA sequence is missing. And it’s exactly the same nucleotide missing in other primates. This shows that the mutation that destroyed our ability to make vitamin C was present in the ancestor of all primates, and was passed on to its descendants. The inactivation of GLO in guinea pigs happened independently, since it involves different mutations. It’s highly likely that since fruit bats, guinea pigs, and primates got plenty of vitamin C in their diet, there was no penalty for inactivating the pathway that made it. This could even have been beneficial since it eliminated a protein that might have been costly to produce.

A dead gene in one species that is active in its relatives is evidence for evolution, but there’s more. When you look at ΨGLO in living primates, you find out that its sequence is more similar between close relatives than between more distant ones. The sequence of human and chimp ΨGLO, for example, resemble each other closely, but differ more from the ΨGLO of orangutans which are more distant relatives. What’s more, the sequence of guinea pig ΨGLO is very different from that of all primates.

Only evolution and common ancestry can explain these facts. All mammals inherited a functional copy of the GLO gene. About 40 million years ago, in the common ancestor of all primates, a gene that was no longer needed was inactivated by mutation. All primates inherited that same mutation. After GLO was silenced, other mutations continued to occur in the gene that was no longer expressed. These mutations accumulated over time — they are harmless if they occur in genes that are already dead — and were passed on to descendant species. Since closer relatives share a common ancestor more recently, genes that change in a time-dependent way follow the pattern of common ancestry, leading to DNA sequences more similar in close than in distant relatives. This occurs whether or not a gene is dead. The sequence of ΨGLO in guinea pigs is so different because it was inactivated independently, in a lineage that had already diverged from that of primates. And ΨGLO is not unique in showing such patterns: there are many other such pseudogenes.1

The above is a compelling example demonstrating that we share a common ancestor with apes and monkeys. However, it arguably isn’t the most compelling example serving as evidence for evolution. Another example of such a gene demonstrates that we descend from egg-laying ancestors. Dennis Venema, Biologist at Trinity Western University, stated the following:

Common ancestry also predicts that, beyond human-chimpanzee common ancestry, the common primate ancestor also shares ancestry with other vertebrates in the more distant past. For example, evolutionary theory predicts that humans, like all vertebrates, are descended from egg-laying ancestors. As with all placental mammals, humans do not use egg yolk as a source of nutrition for their embryos. Other vertebrates such as fish and birds do employ egg yolk, as do a small number of extant mammals such as the platypus.

They found that these genes were present side-by-side and functional in the human genome; then they performed an examination of human sequence between them. As expected, the heavily mutated, pseudogenized sequence of the vitellogenin gene was present in the human genome at this precise location. The human genome thus contains the mutated remains of a gene devoted to egg yolk formation in egg-laying vertebrates at the precise location predicted by shared synteny derived from common ancestry.2

Another line of evidence for evolution comes from molecular biology, namely endogenous retroviruses. In humans, “endogenous retroviruses (HERVs) represent footprints of previous retroviral infection and have been termed “fossil viruses.”3 Also, ” it has been shown that the human genome contains numerous ERVs (HERVs) distributed in several multigenic families comprising a few to several hundreds elements (26, 45, 48). These elements are hallmarks of ancient infections of the germ line by retroviruses which have thereafter been “endogenized” and can be used as molecular markers of evolution.”4

Someone who doesn’t believe in evolution needs to offer alternative explanations for these facts. Their probable next move is predictable: indulge their confirmation bias by consulting creationist and intelligent design websites. Those sites will certainly have “refutations” of these facts, but keep in mind, having a Ph.D. doesn’t imply that one has expertise even on matters unrelated to what one studied. In other words, a Ph.D. in law doesn’t mean one can speak with authority on biology; a Ph.D. in biochemistry doesn’t mean one can speak with authority on physics. This is a common mistake made by creationists: anyone with a Ph.D. is an authority on absolutely anything they purport to be an expert in. Donald Prothero, who was a Professor geology and paleontology for 35 years, states the following:

One of the principal symbols of authority in scholarship and science is the Ph.D. degree. But you don’t need a Ph.D. to do good science, and not all people who have Ph.D.s are good scientists either. As those of us who have gone through the ordeal know, a Ph.D. only proves that you can survive a grueling test of endurance in doing research and writing a dissertation on a very narrow topic. It doesn’t prove that you are smarter than anyone else or more qualified to render an opinion than anyone else. Because earning a Ph.D. requires enormous focus on a specific area, many people with that degree have actually lost a lot of their scholarly breadth and knowledge of other fields in the process of focusing on their theses.

In particular, it is common for people making extraordinary claims (like creationism or alien abductions or psychic powers) to wear Ph.D. (if they have one) like a badge, advertise it prominently on their book covers, and feature it in their biographies. They know that it will impress and awe the listener or reader into thinking they are smarter than anyone else or more qualified to pronounce on a topic. Nonsense! Unless the claimant has earned a Ph.D. in the subject being discussed, the degree is entirely irrelevant to the controversy. For example, leading creationists include Duane Gish, who has a doctorate in biochemistry, and the late Henry Morris, who had a Ph.D. in hydraulic engineering. However, they both earned their degrees almost 50 years ago, so they are not likely to be up-to-date on these rapidly changing fields that they have not practiced in decades. If they stuck to discussing just those topics, they might be halfway believable, but all their criticisms focus on the fossil record, geology, thermodynamics, and so on—topics in which they have absolutely no first-hand experience, published research, or training. Their entire knowledge of these fields (vividly demonstrated by reading their books) consists of skimming and misquoting popular books by real experts in those fields who did the actual work, not going out and doing the research themselves or publishing in peer-reviewed journals. They are no more qualified to comment on paleontology, geology, or thermodynamics than they are qualified to critique music theory! Yet they always flaunt their Ph.D.s to awe the masses and try to intimidate their opponents. The same goes for creationists like Jonathan Sarfati (physical chemistry), Michael Behe (biochemistry), and Jonathan Wells (cell biology)—none of those subjects gives them ANY background in fossils or paleontology, and none has published in any peer-reviewed paleontological journals, so they are complete amateurs when it comes to fossils.5

Given this, one can’t trust any purported authority. One must consult actual experts. Going back to what was mentioned earlier, the issue all creationists and ID advocates have, is that they have a misunderstanding of science. The Christian persecution complex is palpable among such people. They honestly and generally believe that their ideas are being suppressed by the scientific community, a sentiment overtly present in Expelled: No Intelligence Allowed. That sentiment is, however, wrong since it has no place in science. Carl Sagan said it best: “The suppression of uncomfortable ideas may be common in religion or in politics, but it is not the path to knowledge, and there’s no place for it in the endeavor of science.”6

Therefore, it is something about creationism and ID that exempt them from science. The reason they’re exempt is not simply because they’re religiously motivated views, but because they’re akin to astrology, homeopathy, and alchemy—i.e. they are pseudoscience. Jack Ritchie puts it succinctly:

Science is a self-critical enterprise. It provides resources for criticizing itself and other disciplines. We have good and obvious reasons to exclude topics such as astrology or creation science. These disciplines are not successful by their own lights. Astrologers do not accurately predict people’s future on the basis of planetary motions. Advocates of intelligent design, whatever the merits of the problems they raise for various parts of the theory of evolution, have no alternative scientific story to put in its place; they have no suggestion as to how to undertake research into the nature of the “intelligent designer.” Science is different. The sciences have made progress—at least by their own lights. Physicists know more about the subatomic realm than before. No doubt the Large Hadron Collider will enhance that process. Evolutionary biologists know more about the evolutionary process than Darwin. Good science is, furthermore, rich in unsolved problems that this deeper knowledge throws up. We don’t need any general definitions or criteria of what science is to make these points.7

The lack of success of these views is literally the tip of the iceberg. That they’re not successful isn’t what determines that they’re pseudoscience. Pick any of the demarcation theories put forth by philosophers of science and you’ll find that creationism and ID don’t meet the requirements to pass as science. Take, for example, Popper’s falsification. Can we falsify the intelligent designer who, according to many ID advocates, is the Judeo-Christian god? What matters here is not whether a naturalist or an atheist can falsify him. What matters is whether ID advocates are willing to attempt falsification of the intelligent designer. Since their view is rooted in religion, we can be reasonably certain that they’re not going to attempt to falsify the intelligent designer.

Let’s assume, however, that Popper’s falsification isn’t a good marker of demarcation. Let’s instead go with Kuhn’s paradigm shifts. Let’s assume that creationist and ID advocates try for centuries to locate this intelligent designer or creator. Will they put a new theory in place and allow their enterprise to go through a paradigm shift? In other words, will they, like early chemists who discarded Phlogiston theory and introduced theories that better describe the phenomena in question, introduce a new theory that perhaps eliminates an intelligent designer or creator altogether? Again, we can reasonably expect that no matter the evidence, no matter how stacked the odds are, creationists and ID advocates will not discard their current theory in favor of more tenable ones.

Let’s set Kuhn aside. Perhaps his demarcation marker is wrong. Let’s instead look at creationism and ID from the point of view of Lakatos’ research programmes. Lakatos posited that within normal science there are research programmes. The aim of science isn’t hypotheses in isolation or trial and error or conjectures followed by refutations. According to Lakatos, the reason Copernicanism succeeded where Ptolemy’s astronomy failed is because Ptolemy’s astronomy lagged behind as a research programme. The facts, especially after Galileo, supported heliocentrism rather than Ptolemy’s geocentrism, which featured epicycles. Are creationism or ID viable research programmes? No because their so called scientists are not doing normal science. Furthermore, they have no heuristic that serves as a problem-solving mechanism. Therefore, on Lakatos’ view, creationism and ID don’t qualify as science.

With this brief survey of demarcation theories in the philosophy of science, one can see that creationism and ID don’t qualify as science under any of these theories. That’s a problem. It follows that creationism and ID are not suppressed. Rather, it’s that they don’t qualify as scientific theories. Their proponents don’t participate in normal science. They have no research programme in place. They have no interest in falsifying their theory. ID and creationism do not belong in the science classroom and definitely not in a scientific discussion.

Given the case above, creationism and ID should be rejected. They are pseudoscientific theories. Even if they could be falsified, proponents of ID or creationism have no interest in falsifying them. This is due to the fact that advocates of these theories are not practicing normal science. As we can gather from what Prothero said, creationist and ID advocates mislead people with Ph.D.s in normal sciences. However, some of these fields progress rapidly and they are thus required to stay up to date on the changes in their field. This is usually not the case given that some of these people received their Ph.D.s literal decades ago. Therefore, their authority is dubious and upon closer examination, entirely lacking. These purported experts cannot be trusted. Yet this isn’t the reason evolution should be accepted. The reasons outlined above are great starting points. The experts cited are also trustworthy scholars who have done far more work in their respective fields than I was able to showcase here. My hope is that readers who are currently evolution denialists make the choice of doing honest research and coming away with a level of understanding they currently lack.